CN112388617A - Lower limb exoskeleton robot - Google Patents
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- CN112388617A CN112388617A CN202011399567.2A CN202011399567A CN112388617A CN 112388617 A CN112388617 A CN 112388617A CN 202011399567 A CN202011399567 A CN 202011399567A CN 112388617 A CN112388617 A CN 112388617A
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- 210000003141 lower extremity Anatomy 0.000 title claims abstract description 39
- 210000004394 hip joint Anatomy 0.000 claims abstract description 143
- 210000000629 knee joint Anatomy 0.000 claims abstract description 70
- 210000000544 articulatio talocruralis Anatomy 0.000 claims abstract description 53
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 34
- 210000000689 upper leg Anatomy 0.000 claims abstract description 20
- 230000001360 synchronised effect Effects 0.000 claims abstract description 10
- 210000002683 foot Anatomy 0.000 claims description 30
- 238000005452 bending Methods 0.000 claims description 24
- 210000001699 lower leg Anatomy 0.000 claims description 20
- 229920001971 elastomer Polymers 0.000 claims description 16
- 239000000806 elastomer Substances 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 13
- 210000002414 leg Anatomy 0.000 claims description 6
- 230000000712 assembly Effects 0.000 claims description 5
- 238000000429 assembly Methods 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 238000012938 design process Methods 0.000 claims description 4
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000006073 displacement reaction Methods 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 claims description 2
- 238000013461 design Methods 0.000 abstract description 19
- 244000309466 calf Species 0.000 abstract description 3
- 230000008878 coupling Effects 0.000 abstract description 2
- 238000010168 coupling process Methods 0.000 abstract description 2
- 238000005859 coupling reaction Methods 0.000 abstract description 2
- 210000003205 muscle Anatomy 0.000 abstract description 2
- 230000033001 locomotion Effects 0.000 description 22
- 238000004458 analytical method Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 210000003423 ankle Anatomy 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000005381 potential energy Methods 0.000 description 4
- 230000037396 body weight Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000013536 elastomeric material Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 210000003127 knee Anatomy 0.000 description 1
- 235000001968 nicotinic acid Nutrition 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 210000002435 tendon Anatomy 0.000 description 1
- 210000003371 toe Anatomy 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/0006—Exoskeletons, i.e. resembling a human figure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/02—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type
- B25J9/04—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type by rotating at least one arm, excluding the head movement itself, e.g. cylindrical coordinate type or polar coordinate type
- B25J9/045—Polar coordinate type
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Abstract
The invention discloses a lower limb exoskeleton robot. The hip joint design of the existing exoskeleton robot has the problems of complex structure, low coupling with the human body structure and the like, and the knee joint design is not always subjected to stress balance check. The hip joint comprises a hip joint connecting rod, a tapered roller bearing, a hip joint harmonic reducer, a hip joint servo motor, a hip joint shaft, a hip joint rotating frame and an elastic body; the knee joint comprises a thigh supporting piece, a knee joint harmonic reducer, a knee joint servo motor, a driving shaft, a driving belt wheel, a synchronous belt, a driven shaft and a driven belt wheel; the ankle joint includes a calf support, an ankle joint axis, a spring assembly, and a sole plate. According to the invention, the structural design is carried out on each joint of the lower limb exoskeleton robot according to the rotation angles of hip joints and ankle joints and the stress condition of lower limb muscles when a person walks, so that the lower limb exoskeleton robot disclosed by the invention is more in line with the real walking posture required by a wearer, and the purpose of assisting walking is really realized.
Description
Technical Field
The invention relates to the field of health care instruments and mechanical auxiliary devices, in particular to a lower limb exoskeleton robot.
Background
The exoskeleton robot technology integrates the technologies of machinery, mechanics, sensing, control, information and the like, and provides a wearable mechanical auxiliary device for a user. The exoskeleton robot plays a great role in various fields, so that the development prospect is very wide.
In recent 20 years, the exoskeleton robot is widely used as a human body auxiliary device.
1) In the civil field, the exoskeleton robot can help the old to normally act;
2) in the aspect of medical field, the exoskeleton robot can assist the disabled in normal life and greatly reduce the working pressure of medical staff;
3) in the aspect of military field, the exoskeleton robot can improve the rescue efficiency of a battlefield and help more injured people.
In the 60 s of the 20 th century, the american general electric company first proposed and developed a search for a reinforcement-type exoskeleton robot for enhancing the body function and applied it to the military field, and it was not able to obtain ideal results because it was the initial search for exoskeleton robots. A lower extremity exoskeleton robot was developed in 2004 by the university of california at berkeley university, usa, with an overall mass of about 45kg, and was worn by the wearer while still being able to move freely, even with a load of 35 kg. In the coming years, domestic scholars and various scientific research units gradually start to research exoskeleton robot technology. However, the hip joint design of the existing exoskeleton robot has the problems of complex structure, low coupling with the human body structure and the like, and the stress balance check is not usually carried out during the design of the knee joint.
Disclosure of Invention
The invention aims to provide a lower limb exoskeleton robot aiming at the defects of the prior art.
The lower limb exoskeleton robot consists of a connecting frame and two lower limb exoskeleton; the lower limb exoskeleton mainly comprises hip joints, knee joints and ankle joints. The hip joint comprises a hip joint connecting rod, a tapered roller bearing, a hip joint harmonic reducer, a hip joint servo motor, a hip joint shaft, a hip joint rotating frame and an elastic body; the hip joint shaft is supported on a hip joint connecting rod through a tapered roller bearing, one end of the hip joint shaft is fixed with the output end of the hip joint harmonic reducer, and the other end of the hip joint shaft is fixed with the hip joint rotating frame; the input end of the hip joint harmonic reducer is fixed with the output shaft of the hip joint servo motor; the base body of the hip joint harmonic reducer is fixed with the outer ring of the tapered roller bearing; the seat body of the hip joint servo motor is fixed with the seat body of the hip joint harmonic reducer; the elastic body is fixed with the hip joint rotating frame; the hip joint connecting rod is provided with a hip joint bending travel switch and a hip joint extending travel switch, and the output shaft of the hip joint servo motor is also connected with an encoder. The hip joint connecting rods of the hip joints in the lower limb exoskeletons are respectively fixed with the two ends of the connecting frame.
The knee joint comprises a thigh supporting piece, a knee joint harmonic reducer, a knee joint servo motor, a driving shaft, a driving belt wheel, a synchronous belt, a driven shaft and a driven belt wheel; the top of the thigh support is fixed with the elastic body; the driving shaft and the thigh supporting part form a revolute pair and are fixed with the output end of the knee joint harmonic reducer; the input end of the knee joint harmonic reducer is fixed with the output shaft of the knee joint servo motor; the seat body of the knee joint harmonic reducer is fixed with the thigh supporting part; the base body of the knee joint servo motor is fixed with the base body of the knee joint harmonic reducer; the driving belt wheel is fixed on the driving shaft and is connected with the driven belt wheel fixed on the driven shaft through a synchronous belt; the driven shaft and the bottom of the thigh supporting part form a revolute pair; the thigh supporting piece is provided with a knee joint bending travel switch and a knee joint extending travel switch, and an output shaft of the knee joint servo motor is also connected with an encoder.
The ankle joint comprises a shank support part, an ankle joint shaft, a spring assembly and a foot bottom plate; the top of the shank support piece is fixed with the driven shaft; the ankle joint shaft and the bottom of the shank support part form a revolute pair; the rear end of the foot bottom plate is fixed with the ankle joint shaft, and the middle part of the foot bottom plate is connected with the shank support piece through two spring assemblies which are arranged in parallel; the spring assembly consists of a sliding rod, a spring and a sliding sleeve; one end of the sliding rod is hinged with the crus supporting piece, and the other end of the sliding rod and one end of the sliding sleeve form a sliding pair; the other end of the sliding sleeve is hinged with the sole plate.
The knee joint servo motor and the hip joint servo motor are controlled by a controller, and the hip joint bending travel switch, the hip joint extension travel switch, the knee joint bending travel switch, the knee joint extension travel switch and the signal output ends of the two encoders are connected with the controller.
The dimension design process of the elastomer is as follows:
designing the bending angle of the elastic body to be-45 degrees, designing the torsion angle to be-30 degrees, setting a as the width of the elastic body, b as the thickness of the elastic body, c as the height of the elastic body, q as the uniformly distributed load acted on the elastic body by the side, and establishing the maximum linear displacement Y of the elastic body according to a material mechanics formulamaxExpression:
wherein E is the elastic modulus of the elastomer material, and the section inertia moment I is expressed as follows:
when the bending angle of the elastic body is 45 degrees, the straight line distance between two ends of the elastic body is less than or equal to c, then:
Ymax≤c sin45° (3)
by external forces M1The following equation is established:
wherein m is the sum of the mass of the knee joint, the ankle joint, the human leg and the human foot, g is the acceleration of gravity, and L is1For the knee jointAnd the distance from the center of mass of the ankle joint to the top of the elastomer.
The combined vertical type (1), (2), (3) and (4) are obtained
3mgL1c≤Eab3sin45° (5)
Since the maximum value of the torsion angle is designed to be pi/6, the torsion angle is designed according to the mechanics of materials
The formula establishes the following inequality:
wherein G is the shear modulus of the elastomer material, T is the torque applied when the elastomer is twisted, and the designed maximum bearable torque is 700N cm.
And selecting specific values of the width a and the thickness b of the elastic body, and respectively substituting the specific values into the formula (5) and the formula (6) to obtain the value range of the height c of the elastic body.
Wherein, the ratio of the equivalent elastic coefficient of the two springs in the ankle joint to the length of the sole plate is designed as follows:
torque T of front end of foot bottom plate in exoskeleton with ground facing rear lower limbsHThe expression is as follows:
TH＝FJLJcosδ (7)
wherein, FJIs the reaction force of the ground to the front end of a foot bottom plate in the exoskeleton of the lower limbs at the rear part, FJ＝1.2m0g，m0Delta is the included angle between the front end of the sole plate of the exoskeleton of the lower limbs at the rear part and the surface of the central axis of the hip joint shaft and the vertical surface passing through the central axis of the hip joint shaft, and L is the body weightJThe length of the sole plate.
To balance the moments, the two spring assemblies in the rear lower extremity exoskeleton also provide a torque ksα, and has the following relationship:
TH＝ksα (8)
wherein k issIs the equivalent spring constant, k, of the two springss2k, k is the elastic coefficient of one spring; alpha is an included angle between the plane passing through the rear end of the sole plate of the rear lower limb exoskeleton and the central axis of the hip joint shaft and the vertical plane passing through the central axis of the hip joint shaft, and the value of alpha is 13-15 degrees.
And according to FJThe force system of the work is balanced, and the following results are obtained:
then, the following steps are obtained:
wherein v is the walking speed, v is the value in 1.1-1.25 m/s, and LTThe sum of the center distance between the hip joint shaft and the driven shaft and the center distance between the driven shaft and the ankle joint shaft;
united type (7), formula (8) and formula (10), get:
when the walking speed v of the person is constant, δ is regarded as 0, and the sole plate ground clearance angle β is regarded as α, then the walking speed v is obtained
The equivalent elastic coefficients of the two springs and the length L of the sole plateJIn a ratio of
Wherein
Preferably, the ankle joint shaft is supported at the bottom of the shank support part through a tapered roller bearing, and two ends of the ankle joint shaft are provided with bearing blank caps; the bearing blank cap is fixed with the shank support piece and axially positions the tapered roller bearing for supporting the ankle joint shaft.
The invention has the following beneficial effects:
according to the invention, the structural design is carried out on each joint of the lower limb exoskeleton robot according to the rotation angles of hip joints and ankle joints and the stress condition of lower limb muscles when a person walks, so that the lower limb exoskeleton robot disclosed by the invention is more in line with the real walking posture required by a wearer, and the purpose of assisting walking is really realized. Wherein, the flexible technology is applied when the hip joint structure, and the elastic body has the characteristic of bidirectional bending and torsion, and is exactly corresponding to the passive freedom degrees of abduction and adduction movement of the frontal plane of the hip joint and the external rotation and internal rotation movement of the horizontal plane; in addition, the flexion and extension movements of the hip joint in the sagittal plane are designed as active degrees of freedom, corresponding to the flexion and extension movements in the sagittal plane, and the hip joint is finally designed as three degrees of freedom: the sagittal plane flexion and extension movement, the frontal plane abduction or adduction movement and the horizontal plane external rotation or internal rotation movement can simplify the complex design structure in the current market and complete the design optimization of the hip joint structure.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic structural view of a hip joint according to the present invention;
FIG. 3 is a schematic view of the knee joint according to the present invention;
FIG. 4 is a schematic structural view of an ankle joint according to the present invention;
FIG. 5 is a graph illustrating the loading and deflection analysis of the elastomer at the frontal plane in accordance with the present invention;
FIG. 6 is a force analysis diagram of the ankle joint of the present invention.
In the figure: 1. the hip joint comprises a hip joint connecting rod, 2. a tapered roller bearing, 3. a hip joint harmonic reducer, 4. a hip joint servo motor, 5. a hip joint shaft, 6. a hip joint rotating frame, 7. an elastic body, 8. a thigh supporting piece, 9. a knee joint harmonic reducer, 10. a knee joint servo motor, 11. a driving belt pulley, 12. a synchronous belt, 13. a driven belt pulley, 14. a shank supporting piece, 15. a bearing blank cap, 16. a spring assembly, 17. a sole plate.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the lower extremity exoskeleton robot consists of a connecting frame and two lower extremity exoskeletons; the lower limb exoskeleton mainly comprises hip joints, knee joints and ankle joints.
As shown in fig. 2, the hip joint comprises a hip joint connecting rod 1, a tapered roller bearing 2, a hip joint harmonic reducer 3, a hip joint servo motor 4, a hip joint shaft 5, a hip joint rotating frame 6 and an elastic body 7; the hip joint shaft 5 is supported on the hip joint connecting rod 1 through a tapered roller bearing 2 (the outer ring of the tapered roller bearing 2 is matched with the hip joint connecting rod 1, the inner ring is matched with the hip joint shaft 5), one end of the hip joint shaft is fixed with the output end of the hip joint harmonic reducer 3, and the other end of the hip joint shaft is fixed with the hip joint rotating frame; the input end of the hip joint harmonic reducer 3 is fixed with the output shaft of the hip joint servo motor 4; the seat body of the hip joint harmonic reducer 3 is fixed with the outer ring of the tapered roller bearing 2; the base body of the hip joint servo motor 4 is fixed with the base body of the hip joint harmonic reducer 3; the elastic body 7 is fixed with the hip joint rotating frame 6; the hip joint connecting rod 1 is provided with a hip joint bending travel switch and a hip joint extending travel switch, and the output shaft of the hip joint servo motor 4 is also connected with an encoder. The hip joint connecting rods 1 of the hip joints in the lower extremity exoskeletons are respectively fixed with the two ends of the connecting frame. The hip joint can be approximated as a ball joint, designed for three degrees of freedom of motion: flexion and extension movements in the sagittal plane, abduction or adduction movements in the frontal plane, and external or internal rotation movements in the horizontal plane. The flexion and extension movement on the sagittal plane is realized by driving a hip joint shaft 5 by a hip joint servo motor 4, and the exoskeleton does not exceed the flexion and extension range of the hip joint of a human body by adopting double limiting of hard limiting (a hip joint bending travel switch and a hip joint extension travel switch) and soft limiting (an encoder); when the degree of freedom in the frontal plane and the horizontal plane of the hip joint is designed, the characteristic that the elastic body can be bent and twisted and can bear load is considered, and the elastic body is designed, so that the structural design of the hip joint is simplified.
As shown in fig. 3, the knee joint includes a thigh support 8, a knee joint harmonic reducer 9, a knee joint servo motor 10, a driving shaft, a driving pulley 11, a synchronous belt 12, a driven shaft, and a driven pulley 13; the top of the thigh support 8 is fixed with the elastic body 7; the driving shaft and the thigh supporting part 8 form a revolute pair and are fixed with the output end of the knee joint harmonic reducer 9; the input end of the knee joint harmonic reducer 9 is fixed with the output shaft of the knee joint servo motor 10; the seat body of the knee joint harmonic reducer 9 is fixed with the thigh support part 8; the seat body of the knee joint servo motor 10 is fixed with the seat body of the knee joint harmonic reducer 9; the driving belt wheel 11 is fixed on the driving shaft and is connected with the driven belt wheel 13 fixed on the driven shaft through a synchronous belt 12; the driven shaft and the bottom of the thigh supporting part 8 form a revolute pair; a knee joint bending travel switch and a knee joint extending travel switch are arranged on the thigh supporting part 8, and an output shaft of the knee joint servo motor 10 is also connected with an encoder.
When designing the knee joint structure, the design principle of considering both cost and safety is followed. Based on bionics knowledge, the knee joint has only one degree of freedom in the sagittal plane, and other minor rotational motions can be ignored. The knee joint has the largest power assistance in the human body joint and heavier load, and has larger impact force when the foot touches the ground, the synchronous belt is adopted to drive the rotating shaft (driven shaft) to complete the flexion and extension movement of the knee joint, and the hard limit (knee joint bending travel switch and knee joint extension travel switch) and the soft limit (encoder) are adopted for double limit, so that the exoskeleton does not exceed the flexion and extension range of the human body knee joint. The knee joint servo motor 10 is driven in a synchronous belt transmission mode, so that the structure is simplified, and the characteristics of stable buffering, vibration absorption and transmission and the like are achieved.
As shown in FIG. 4, the ankle joint includes a calf support 14, ankle joint axis, spring assembly 16 and sole plate 17; the top of the shank support part 14 is fixed with the driven shaft; the ankle joint shaft and the bottom of the shank support member form a revolute pair; the rear end of the foot bottom plate 17 is fixed with the ankle joint shaft, and the middle part of the foot bottom plate is connected with the shank support part 14 through two spring components 16 which are arranged in parallel; the spring assembly 16 consists of a sliding rod, a spring and a sliding sleeve; one end of the sliding rod is hinged with the crus supporting piece 14, and the other end of the sliding rod and one end of the sliding sleeve form a sliding pair; the other end of the sliding sleeve is hinged with the foot bottom plate 17.
The knee joint servo motor 10 and the hip joint servo motor are controlled by a controller, and a hip joint bending travel switch, a hip joint extension travel switch, a knee joint bending travel switch, a knee joint extension travel switch and signal output ends of the two encoders are connected with the controller.
As a preferred embodiment, the ankle joint shaft is supported at the bottom of the shank support part through a tapered roller bearing 2, and both ends of the ankle joint shaft are provided with bearing blank caps 15; the bearing cap 15 is fixed to the calf support and axially locates the tapered roller bearing 2 which supports the ankle joint axis.
According to human kinematics analysis, the ankle joint moves mainly in the sagittal plane. Because the ankle joint motion range and the stress are small, the ankle joint motion range and the stress are suitable for adopting the passive degree of freedom. As shown in fig. 4, the spring assembly is combined with the ankle joint shaft, when the feet step on the ground, the gravitational potential energy of the human body is converted into the elastic potential energy of the spring, so that the spring is compressed and contracted, when the feet are lifted, the elastic potential energy is slowly released, the spring is freely restored to the maximum length, and the ankle is stably stressed to achieve the purpose of assisting the ankle to stably and slowly flex and stretch. Because the spring has slower extension speed, the change of the force is more moderate, and the human body can not be injured.
The design process of the hip joint and the ankle joint is as follows:
during the design of the joint structure of the robot, the anthropomorphic design is adopted, namely the consistency of the joint structure design and the human joint motion is kept as much as possible.
1. Hip joint design procedure
Aiming at the phenomenon that the hip joint structure of the robot is designed by applying a flexible technology, the hip joint structure of the robot can be bent and twisted in two directions according to the characteristic that an elastic body has two-way bending and twisting, and the hip joint structure is exactly corresponding to the passive freedom degrees of abduction and adduction motions of the frontal plane of the hip joint and the external rotation and internal rotation motions of the horizontal plane; in addition, the flexion and extension movement of the hip joint in the sagittal plane is designed into active degree of freedom, the hip joint servo motor 4 is utilized to drive the hip joint shaft 5 to rotate, which just corresponds to the flexion and extension movement of the sagittal plane, and finally the hip joint is designed into three degrees of freedom: sagittal plane flexion and extension, frontal plane abduction or adduction, and horizontal plane supination or pronation. Therefore, the complex design structure in the current market can be simplified, and the design optimization of the hip joint structure is completed.
The dimension design process of the elastomer is as follows:
according to the rubber elasticity physics, the bending angle of the elastic body is designed to be-45 degrees, and the torsion angle is designed to be-30 degrees. When bending analysis is performed, the elastic body is regarded as a cantilever beam structure according to a material mechanics simplified model, when a force in the human body side direction acts on the elastic body, the uniform load q (unit N/cm) can be equivalently obtained, and the mechanical sketch of the bending of the elastic body is shown in fig. 5.
Setting a as the width of the elastic body, b as the thickness of the elastic body, c as the height of the elastic body, and the unit of a, b and c is cm. Establishing the maximum linear displacement Y of the elastomer according to a material mechanics formulamax(unit cm) expression:
wherein E is the modulus of elasticity of the elastomeric material, in N/m2；
Moment of inertia in cross section I (unit cm)4) The expression is as follows:
and because when the bending angle of the elastic body is 45 degrees, the straight line distance between two ends of the elastic body is necessarily less than or equal to c, then:
Ymax≤c sin45° (3)
by external forces M1An equation is established, namely:
wherein m is the sum of the mass of the knee joint, the ankle joint, the legs of the human body and the mass of the feet of the human body in kg; m is m1+m2，m1The total mass of the legs and the feet of the human body is obtained, and the value is m when the gender is male according to the value of the gender10The value of sex is m11，m10Taking the average value of the male leg and foot mass, wherein m is taken10＝12kg，m11Taking the average value of the masses of the female leg and foot, wherein m is taken11＝10.5kg；m2The total mass of the knee joint and the ankle joint is kg; g is gravity acceleration in m/s2；L1Is the distance in cm from the center of mass of the knee joint and ankle joint to the top end of the elastic body 7.
The combined vertical type (1), (2), (3) and (4) are obtained
3mgL1c≤Eab3sin45° (5)
g＝9.8m/s2Taking the elastic modulus E of the elastomer material as 6.1 × 106N/m2，m＝22kg，L153.2cm for formula (5):
79.77c≤ab3 (6)
since the maximum value of the torsion angle is designed to be pi/6 (namely 30 degrees), the torsion angle is designed according to the mechanics of materials
The formula establishes the following inequality:
wherein G is the shear modulus of the elastomer material and is 2.39 multiplied by 106N/m2T is the torque applied to the elastic body during torsion, and the maximum allowable torque is 700N cm.
Considering the size of the designed hip joint connector, the width a of the elastomer is 10cm, the thickness b is 5cm, and the formula (7) is substituted, so that:
c≥0.13 (8)
and a 10cm and b 5cm are substituted for formula (6) to give:
c≤15.67 (9)
combining formula (8) and formula (9), and selecting c as 10 cm.
2. Ankle joint design procedure
The human ankle joint mainly moves in the sagittal direction, the motion range and the stress are small, the required driving force is small, the main design principle is to keep balance, and the passive degree of freedom is suitable for being adopted. The ankle joint tendon is used as a passive elastic structure and plays a role of a spring in the walking process, so that the ankle joint is provided with a pair of parallel spring components in the mechanical structure design, and when the ankle joint is not stressed, the spring naturally extends to the maximum length; when forced, the spring is compressed. Therefore, the spring stores energy during the standing stage of the human body, and the exchange of potential energy and kinetic energy can be realized during the walking process.
According to the rod-shaped mechanical analysis model, when the foot is off the ground, the total moment of the ankle is zero, the expression of the ankle torque and the reaction force of the ground to the foot can be obtained, the ratio of the equivalent elastic coefficients of the two springs to the length of the sole plate can be obtained through calculation processing, the ankle joint is designed on the basis of the expression, the joint torque is provided for the exoskeleton robot, and the stable walking of the exoskeleton robot is realized.
As shown in FIG. 6, the torque T at the front end of the foot plate 17 in the ground-to-rear lower extremity exoskeletonHThe expression is as follows:
TH＝FJLJcosδ (10)
wherein, FJFor ground reaction to the front end of foot plate 17 in the rear lower extremity exoskeleton, it has been well studied that the reaction to the toes is about 1.2 times the body weight, and therefore, where F is takenJ＝1.2m0g，m0The value is m when the sex is male01The value of sex is m02Where m is01Taking the average value of the male body weight of 60kg, m02Taking the average value of the female body weight as 55kg, wherein delta is an included angle between the plane passing through the front end of the sole plate 17 of the rear lower limb exoskeleton and the central axis of the hip joint shaft 5 and the vertical plane passing through the central axis of the hip joint shaft 5, and L isJThe length of the foot plate 17.
To balance the moments, the two spring assemblies in the rear lower extremity exoskeleton also provide a torque ksα, and has the following relationship:
TH＝ksα (11) wherein ksIs the equivalent spring constant, k, of the two springss2k, k is the elastic coefficient of one spring; alpha is an included angle (generally, a value is 13-15 degrees) between the rear end of a sole plate 17 passing through the rear lower limb exoskeleton and a plane passing through the central axis of the hip joint shaft 5 and a vertical plane passing through the central axis of the hip joint shaft 5; the force analysis of the rear end point A of the foot bottom plate 17 of the rear lower extremity exoskeleton is shown in figure 6.
And according to FJThe force system of the work is balanced, and the following results are obtained:
v is the walking speed (generally, the value is 1.1-1.25 m/s), and LTThe sum of the center distance between the hip joint shaft 5 and the driven shaft and the center distance between the driven shaft and the ankle joint shaft;
the united type (10), the formula (11) and the formula (13) are as follows:
obtaining:
when the walking speed v of the person is constant, the foot length is approximately equal to half the step length, wherein δ is equal to 0, and the ground clearance angle β of the foot bottom plate 17 is equal to α, then the walking speed v is obtained
The equivalent spring constant of the two springs and the length L of the sole plate 17JIn a ratio of
Wherein
Claims (2)
1. The lower limb exoskeleton robot consists of a connecting frame and two lower limb exoskeleton, and is characterized in that: the lower limb exoskeleton mainly comprises hip joints, knee joints and ankle joints; the hip joint comprises a hip joint connecting rod, a tapered roller bearing, a hip joint harmonic reducer, a hip joint servo motor, a hip joint shaft, a hip joint rotating frame and an elastic body; the hip joint shaft is supported on a hip joint connecting rod through a tapered roller bearing, one end of the hip joint shaft is fixed with the output end of the hip joint harmonic reducer, and the other end of the hip joint shaft is fixed with the hip joint rotating frame; the input end of the hip joint harmonic reducer is fixed with the output shaft of the hip joint servo motor; the base body of the hip joint harmonic reducer is fixed with the outer ring of the tapered roller bearing; the seat body of the hip joint servo motor is fixed with the seat body of the hip joint harmonic reducer; the elastic body is fixed with the hip joint rotating frame; the hip joint connecting rod is provided with a hip joint bending travel switch and a hip joint extending travel switch, and an output shaft of the hip joint servo motor is also connected with an encoder; hip joint connecting rods of hip joints in the lower limb exoskeleton are respectively fixed with two ends of the connecting frame;
the knee joint comprises a thigh supporting piece, a knee joint harmonic reducer, a knee joint servo motor, a driving shaft, a driving belt wheel, a synchronous belt, a driven shaft and a driven belt wheel; the top of the thigh support is fixed with the elastic body; the driving shaft and the thigh supporting part form a revolute pair and are fixed with the output end of the knee joint harmonic reducer; the input end of the knee joint harmonic reducer is fixed with the output shaft of the knee joint servo motor; the seat body of the knee joint harmonic reducer is fixed with the thigh supporting part; the base body of the knee joint servo motor is fixed with the base body of the knee joint harmonic reducer; the driving belt wheel is fixed on the driving shaft and is connected with the driven belt wheel fixed on the driven shaft through a synchronous belt; the driven shaft and the bottom of the thigh supporting part form a revolute pair; a knee joint bending travel switch and a knee joint extending travel switch are arranged on the thigh supporting piece, and an output shaft of the knee joint servo motor is also connected with an encoder;
the ankle joint comprises a shank support part, an ankle joint shaft, a spring assembly and a foot bottom plate; the top of the shank support piece is fixed with the driven shaft; the ankle joint shaft and the bottom of the shank support part form a revolute pair; the rear end of the foot bottom plate is fixed with the ankle joint shaft, and the middle part of the foot bottom plate is connected with the shank support piece through two spring assemblies which are arranged in parallel; the spring assembly consists of a sliding rod, a spring and a sliding sleeve; one end of the sliding rod is hinged with the crus supporting piece, and the other end of the sliding rod and one end of the sliding sleeve form a sliding pair; the other end of the sliding sleeve is hinged with the sole plate;
the knee joint servo motor and the hip joint servo motor are controlled by a controller, and a hip joint bending travel switch, a hip joint extension travel switch, a knee joint bending travel switch, a knee joint extension travel switch and signal output ends of the two encoders are connected with the controller;
the dimension design process of the elastomer is as follows:
designing the bending angle of the elastic body to be-45 degrees, designing the torsion angle to be-30 degrees, setting a as the width of the elastic body, b as the thickness of the elastic body, c as the height of the elastic body, and q as the uniformly distributed load acting on the elastic body at the side, and establishing the elastic body according to a material mechanics formulaMaximum linear displacement Y of elastomermaxExpression:
wherein E is the elastic modulus of the elastomer material, and the section inertia moment I is expressed as follows:
when the bending angle of the elastic body is 45 degrees, the straight line distance between two ends of the elastic body is less than or equal to c, then:
Ymax≤csin45° (3)
by external forces M1The following equation is established:
wherein m is the sum of the mass of the knee joint, the ankle joint, the human leg and the human foot, g is the acceleration of gravity, and L is1The distance from the center of mass of the knee joint and the ankle joint to the top end of the elastic body;
the combined vertical type (1), (2), (3) and (4) are obtained
3mgL1c≤Eab3sin45° (5)
Since the maximum value of the torsion angle is designed to be pi/6, the torsion angle is designed according to the mechanics of materials
The formula establishes the following inequality:
wherein G is the shear modulus of the elastomer material, T is the torque applied when the elastomer is twisted, and the designed maximum bearable torque is 700N cm;
selecting specific values of the width a and the thickness b of the elastic body, and respectively substituting the specific values into a formula (5) and a formula (6) to obtain a value range of the height c of the elastic body;
wherein, the ratio of the equivalent elastic coefficient of the two springs in the ankle joint to the length of the sole plate is designed as follows:
torque T of front end of foot bottom plate in exoskeleton with ground facing rear lower limbsHThe expression is as follows:
TH＝FJLJcosδ (7)
wherein, FJIs the reaction force of the ground to the front end of a foot bottom plate in the exoskeleton of the lower limbs at the rear part, FJ＝1.2m0g，m0Delta is the included angle between the front end of the sole plate of the exoskeleton of the lower limbs at the rear part and the surface of the central axis of the hip joint shaft and the vertical surface passing through the central axis of the hip joint shaft, and L is the body weightJThe length of the sole plate;
to balance the moments, the two spring assemblies in the rear lower extremity exoskeleton also provide a torque ksα, and has the following relationship:
TH＝ksα (8) wherein ksIs the equivalent spring constant, k, of the two springss2k, k is the elastic coefficient of one spring; alpha is an included angle between the rear end of a sole plate passing through the rear lower limb exoskeleton and a plane passing through the central axis of the hip joint shaft and a vertical plane passing through the central axis of the hip joint shaft, and alpha is taken out at 13-15 degrees;
and according to FJThe force system of the work is balanced, and the following results are obtained:
then, the following steps are obtained:
whereinV is the walking speed, v is the value in 1.1-1.25 m/s, LTThe sum of the center distance between the hip joint shaft and the driven shaft and the center distance between the driven shaft and the ankle joint shaft;
united type (7), formula (8) and formula (10), get:
when the walking speed v of the person is constant, δ is regarded as 0, and the sole plate ground clearance angle β is regarded as α, then the walking speed v is obtained
The equivalent elastic coefficients of the two springs and the length L of the sole plateJIn a ratio of
Wherein
2. The lower extremity exoskeleton robot of claim 1, wherein: the ankle joint shaft is supported at the bottom of the shank support part through a tapered roller bearing, and bearing caps are arranged at two ends of the ankle joint shaft; the bearing blank cap is fixed with the shank support piece and axially positions the tapered roller bearing for supporting the ankle joint shaft.
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